System for controlling power consumption at a user of electric power

ABSTRACT

The invention relates to a system for controlling power consumption at a user of electric power, especially a dwelling supplies with power from a power plant. The invention is characterized in that the control unit is a main unit arranged to control the power consumption also based on an estimate of a historical consumption pattern at the user, so that the instantaneous consumption is reduced both in the periods in which the power load at the user is highest, and in the periods in which the historical consumption pattern of the user dictates that there is a high load, and that the main unit user is arranged to distribute the power consumption by means of a random function distributing the connection of the power consuming units over a given time interval, the random function being independent of energy plants and other users.

BACKGROUND OF THE INVENTION

The invention relates to a system for controlling power consumption at auser of electric power, especially a dwelling supplied with power from apower plant, comprising a control unit installed at the user and havinga programmable memory for storage of data for controlling the powerconsumption, parameter-sensing sensors for the supply of input signalsto the control unit, an electric meter communicating with the controlunit for measuring the total instantaneous consumption of the user, anda number of addressable function nodes connected between the controlunit and the various loads and being in both-way communication with thecontrol unit, for connection and disconnection of power-consuming unitsunder the control thereof, the memory of the control unit containing aprogram for controlling the power consumption based on an estimate ofthe instantaneous consumption, and the control unit being arranged totransmit addressed messages to the function nodes, so that only thenodes with the correct address receive the current messages and executeload-affecting actions based on the message content, to thereby reducethe instantaneous consumption.

For dwellings and households there have been launched, during the lateryears, a number of energy-economizing products and systems reducing theconsumption of electric energy for the household. Generally, thesesystems are based on temperature or sequence control of electricappliances used for heating, for instance electric heating stoves. Inthis manner the power consumption is reduced at the end user, but thepower consumption is not reduced during the period in which the load islargest.

Statistical data regarding the energy consumption in private householdsshow that there is a higher consumption in some time periods during theday. These time periods are in the morning hours and in theafternoon/evening, respectively, and more specifically in the periods6-10 and 16-23. Within a distribution area, the power load in themorning hours may rise from e.g. 825 MW to about 1100 MW around 8o'clock, to sink thereafter before a new peak occurs in the eveningaround 19 o'clock. The most important thing is not the time at which theload peaks occur, but that they appear at intervals with a high degreeof regularity in the course of the morning hours and theafternoon/evening. The load profile is approximately equal through thewhole year, a normal year being assumed, i.e. that there are no extremechanges in temperature or in the prices of electricity.

From the collected statistical data, the energy plants know the loadhistories and prognosticate future consumption from predefinedconsumption curves and within given safety margins.

Today there exist different types of systems in which the powerconsumption at the subscribers of a power company is controlled. Thetraditional “Demand Side Management” or DSM method is based on two-waycommunication between energy supplier (energy plant) and subscribers. Inthese systems, the framework conditions and the parameters for how theconsumption in the dwelling of the subscriber is to be controlled, areset by the power plant. This method has the weakness that the system isbased on often occurring input of regulating control data from the powercompany. These control data then will be based on the consumptionpattern of the total subscriber mass of the power company. Thisconsumption pattern may, however, deviate strongly from the consumptionpattern of the individual household, so that the achieved control of thepower consumption in many cases will not be optimal, considered inrelation to the consumption pattern and the current power consumption atthe individual subscriber or user.

Several other known methods and systems remedy this weakness, eitherintendedly or unintendedly, by putting in control mechanisms seeking anoptimum local control at the subscribers. As examples hereof, referencecan be made to U.S. Pat. Nos. 5,436,510, 4,510,398 and EP 0 717 487 A1disclosing systems of the introductorily stated type. The local controlaccording to these systems usually is based on said framework conditionswhich are given by the power company, but to a higher extent thantraditional DSM control is able to secure a better utilization of theenergy at the individual subscribers. Common to these systems is,however, that the dynamic load control limits itself to see to it thatthe power consumption at the subscriber does not exceed given maximumlimits. The maximum limits may be set by the power company, or they maybe set locally at the subscriber. The systems are quiescent as long asthese limits are not exceeded. This means, for example, that if a givennumber of households at a given time lie closely under these limits, thecollected total consumption for these households will be relativelyhigh. U.S. Pat. No. 5,436,510 and U.S. Pat. No. 4,510,398 in additiondescribe devices seeking to add new loads as long as the totalconsumption is under the given maximum limit. In addition to said totalconsumption problems, this means that the subscriber hardly gets anypleasure from the power control with respect to energy saving.

SUMMARY OF THE INVENTION

On this background it is an object of the invention to provide a systemdistributing the power consumption at a subscriber even if theconsumption at the subscriber does not exceed given maximum limits, sothat, both locally at a subscriber and collectively in a larger user orsubscriber mass, one achieves a more optimum power regulation and asmoother power distribution.

The above-mentioned object is achieved with a system of theintroductorily stated type which, according to the invention, ischaracterized in that the control unit is a main unit arranged tocontrol the power consumption also based on an estimate of a historicalconsumption pattern at the user, so that the instantaneous consumptionis reduced both in the periods in which the power load at the user ishighest, and in the periods in which the historical consumption patternof the user dictates that there is a high load, and that the main unitis arranged to distribute the power consumption by means of a randomfunction distributing the connection of the power-consuming units over agiven time interval, the random function being independent of energyplants and other users.

In the system according to the invention the main unit is arranged todistribute the power consumption in the time periods around global andlocal high load by means of said random function which operates locallyat a subscriber in such a manner that the power consumption is displaceda randomly chosen time interval, to flatten the local power consumptionin addition to the collected or global total consumption for a wholeuser or subscriber mass as seen by the power company. In practice thismeans that one uses the “law of large numbers” to lower the powerconsumption in a larger transformer circuit with many connectedsubscribers. Thus, the system implies that several main units willappear in co-action without knowing about each other, and thereby keepthe power consumption down on a global scale.

The system according to the invention from the starting point is notconnected to an operating central, but is a stand-alone automaticcontrol system monitoring and regulating the power consumption at theend user from a historical consumption pattern established by the enduser/household during a previous time period, together with theinstantaneous consumption, the temperature and other variable inputsignals.

Thus, the load distribution takes place locally in the household and iscontrolled by the main unit (hereafter also called “master”) utilizingsuch parameters as temperature, instantaneous consumption and knownconsumption patterns to accomplish the distribution, based on saidrandom function. This will take place without the comfort being changedin the household. Said parameters are run through a set of rules storedin the program of the master. The program works out prognoses anddistributes the power consumption based on season, day of the week, timeof the day, temperature, the power consumption at the moment and thepower consumption over time. As mentioned, the system operates as aself-contained unit and is not connected to a power plant or anoperating central. Primarily, the system is intended for use inhouseholds, business buildings and other buildings which, for somereason, have a need for releasing and stabilizing the power consumption,so that the load peaks are reduced.

If desired, the system may for example be connected to an operatingcentral by means of, e.g., a both-way communication system. Since thesystem provides for automatic power release in high-load periods and thepower is distributed over the hours around peak load, the load structureis flattened and gets smaller variations. The energy plants then canprognosticate the power consumption with a smaller risk, carry outcost-effective readings, reduce the network loss by means of a smootherload, and also connect the customer/subscriber to themselves by offeringadditional services.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be further described below in connection withexemplary embodiments with reference to the drawings, wherein

FIG. 1 is a diagram showing an example of a load curve, i.e. a curveshowing the load within a network station area distributed over the 24hours of the day;

FIG. 2 is a diagram showing load curves of a household for two differentdays;

FIG. 3 is a block diagram illustrating the system according to theinvention;

FIG. 4 illustrates the distribution of power consumption (load) over atime period under the influence of the random function;

FIG. 5 shows a block diagram of the main unit (master) in the systemaccording to the invention; and

FIG. 6 shows a block diagram of a function node in the system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows the total consumption for a number of end users within anetwork station or distribution area. The illustrated curve represent a“normal” consumption pattern for a user or subscriber group. Since theconsumption pattern reflects a pattern of life, the load peaks may occurat somewhat different times according to where in the country thesubscriber group lives. As appears form the figure, and as mentioned inthe introduction, the load peaks occur during the morning hours and inthe afternoon/evening, in dependence of the life pattern of the usergroup.

Each end user has his own consumption curve. An example of such a curveis shown in FIG. 2 showing load curves a and b for two different days.Each curve may be divided in that each individual power-consuming unitin e.g. a household has its own consumption curve. If the curves for agreat number of end users are summed, one gets a curve approximatelycorresponding to the load curve in FIG. 1.

The life pattern of a household results in a consumption pattern storedin the master of the present system. This consumption may deviatestrongly from the consumption pattern possessed by the great subscribermass, or it may coincide with this consumption pattern during certainperiods. This consumption pattern, which may be designated a historicalconsumption pattern, gives the main unit (master) a certain number ofstored samples, so that it may recognize a consumption pattern and actwith a smaller risk by monitoring and regulating given electricproducts.

In addition to the historical consumption pattern, the master has alearning function resulting in that it learns the life pattern of thehousehold by remembering when the various electric products are used.Further, the master for example remembers that the household preparesdinner around 17.05 o'clock on weekdays. When the time approaches 17o'clock, the master therefore expects that the energy consumption willrise considerably. Since it remembers this, it effects some actionsbefore 17 o'clock, and postpones other actions to a later time, so thatthe peak load does not occur at the same time as for all otherhouseholds/dwellings within a distribution area.

The block diagram in FIG. 3 illustrates the system according to theinvention. The system may be designated an “electronic power limiter”and executes electronic dynamic control of the power consumption at anend user. The system comprises a main unit or master 10, an energy orelectric meter 11, which is connected to the master via an S0 interface,a number of sensors 1, 2, 3, . . . n, and a number of function nodeswhich are designated 4, 5 and 6 and are connected between the master 10and electric products, i.e. the power-consuming units to be controlled.These units in the figure are represented by a block 12, and areotherwise left out in the figure.

The various sensors 1 . . . n provide input signals to the master. Thesesignals for example can be read temperature or other reading values,such as a water reading or the like.

The function nodes 4, 5 and 6 are nodes controlling high-power products.With high-power products there are meant products having a high powerconsumption at the moment. The nodes designated 6 are nodes having nodirect influence on the peak load, because of the fact that the need isa relatively low power consumption when they are on.

The system also comprises electric products which are only monitored,and not controlled, and which are designated 3 in FIG. 3 and areillustrated as hexagonal symbols. For example, it is not desirable tocontrol when a user may use the kitchen range, but it is desirable tomonitor when the range is used, since this often indicates a consumptionpattern. The fact that the user always uses the range (prepares dinner)during, e.g., a time period after 16.30 o'clock, will give the master anindication that other high-power products should be switched off in thisperiod.

All the electric products which can be controlled or monitored, such aswashing machine, kitchen range, percolator, water heater etc., can becategorized according to low, medium or high priority. Which productsare registered in the different categories, varies from household tohousehold, but the priority levels can be described as follows.

“Low priority” comprises products which can be disconnected in shorterperiods, up to several times during the day, without the user noticingthis change. Typical such products are water heater, heating cables andheating stoves.

“Medium priority” comprises products which can be disconnected inperiods with peak load, especially in the periods 6-10 and 16-23.Typical such units may be individual lamps, freezer, asf.

“High priority” comprises products which are used continuously, orproducts which are wanted to be accessible at any time, and which insome cases have a high power consumption. These products are not to becontrolled by any nodes, but are only monitored by reading of the powerconsumption. These are products like kitchen range, washing machine,drying tumbler, electric alarm clock, radio, asf.

The principle of distribution of load under the influence of the randomfunction is shown in FIG. 4. The total time over which the load isdistributed, i.e. the time interval for distribution of load, isdesignated t_(f). There is nothing to prevent defining t_(f) to apply toan infinitely large time interval, so that a load controlling functionwill always be present. The range of definition for peak load isdesignated t_(p), whereas t_(d) is the time period over which the peakload is to be distributed for and after the peak load period. Thus, onehas t_(f)=t_(p)+2·t_(d). Incidental time intervals within the total timeinterval t_(f) are designated t_(i). A time interval t_(i) is the periodin which a power consuming unit is switched on. The random functioncomes into force within the time period t_(f) and is applied to eachindividual unit being in both-way communication with the master. Itassigns to each unit a random or incidental period in which the unit isto be switched off. When this period is over, the unit is switched on,or is allowed to be switched on in the time period with the lengtht_(i). When the period t_(i) is over, the random function is againapplied to the unit which has been switched on. This is repeated for allunits as soon as the time period t_(i) for the individual unit is over.

As an example it is supposed that t_(i)=30 min, and that t_(f)=120 minat an arbitrary time of the day. Further, it is supposed that twopower-consuming units 1 and 2 have been switched on before the entryinto the distribution interval t_(f). As the interval t_(f) is entered,both units will be switched off, and the random function comes intoforce by randomly determining that unit 1 shall be switched off for 15minutes, whereas unit 2 shall be switched off for 30 minutes. After 15minutes have elapsed, unit 1 will be switched on, and it is noted thatthe t_(i) interval for unit 1 has started. After additionally 15 minutesunit 2 is switched on, and it is noted that the t_(i) interval for thisunit has started. When now 15 minutes have elapsed, it will bediscovered that the t_(i) interval for unit 1 has expired since thisunit now has been on for 30 minutes, and the unit is switched off. Therandom function then comes into force once more, and chooses a new timeinterval for how long the unit 1 shall be switched off, for example 10minutes. After these 10 minutes, unit 1 is again switched on, and it isnoted that still another t_(i) interval has started for unit 1. It nowlasts only five minutes before unit 2 is switched off, and the randomfunction comes into force and chooses an incidental period for how longunit 2 is to be switched off. This will be repeated for all units in thesystem during the whole interval t_(f). Locally, at a subscriber, theconsumption then will get displaced, and one obtains both a power and anenergy profit for the time in which the units are switched off. Asregards the global power saving, one has that the arithmetic mean of anumber of numerals is equal to the sum of the numerals divided by thenumber. If the numerals are extracted from a uniform distribution, suchas done in the system according to the invention by means of the randomfunction, all numerals must appear with the same frequency when thenumber of numerals approaches infinity. This means that the arithmeticmean is the sum of all numerals in the distribution divided by thenumber of numerals. A distribution from 0 to 30 will have a mean of(0+1+2+ . . . +30)/31=15. As an example in this connection, it isassumed that one has a great number of stoves controlled by the randomfunction used in the system according to the invention. Further, it isassumed that all of these stoves yield 1000 W. If t_(i) is 30 minutesand the random function chooses an incidental numeral between 0 and 30as a disconnection interval, and if one has a control or distributioninterval t_(f) of 60 minutes, the saving will be 1000·15/60=250 Wh. Inaddition, the load will be distributed quite smoothly over the wholetime interval.

FIG. 5 shows a block diagram of the main unit or master 10. The masterconstitutes a node (junction) which is an intelligent unit whichautomatically monitors, controls and checks the consumption and the loadstructure in that it is supplied with measuring data from the electricmeter and from the sensors of the system, and in that it has thepossibility to exchange data regularly itself, without interveningmanually and setting new parameters and other variables.

As appears from the figure, the master comprises an integrated processorunit (CPU) 15, a read only memory (ROM) 16, a random access memory (RAM)17, a number of I/O cards and a clock 18 with real time and calendar.The I/O cards are shown to comprise an SO input circuit 19, an RS232port 20 and an I²C interface 21. This interface comprises inputs 22 forthe supply of signals from the various sensors in the system. Inaddition, there is provided a battery 23, a circuit 24 for galvanicdivision between the mains voltage (220 V) and a low-voltage supplycircuit (15V/300 mA), and a pair of regulators 25 and 26 for the supplyof DC voltages of 5 V and 12 V, respectively.

Communication between the master 10 and the electric product to becontrolled thereby, takes place in that the master transmitsmessages/commands to the function node (4, 5, 6). The nodes constitutesreceivers placed in the contact points between the relevant products andplug outlets in which the products are connected to the mains. Eachmessage contains a special address which is addressed to one or morenodes, so that the nodes know who shall receive the message and reactthereon. Further, the message contains information which is to assistthe node in executing the correct actions.

The communication takes place via existing line structure in thedwelling/building by means of so-called Spread Spectrum Carrier (SSC)signalling. For this purpose, between the processor unit 15 and themains (220V), there are connected an output amplifier 27 and an SSC chip28 for transferring the control signals or messages of the processorunit to the function nodes. The messages are transmitted in a low-levelcommand language called CAL (Common Application Language, ANSI/EIA-600).

The software of the master is stored in the read only memory (ROM) 16,and the variable data which are either given by the end user or obtainedfrom the external sensors, are stored in the random access memory (RAM).The master acts from the set of rules in the software program stored inthe read only memory, and the input signals sent from the random accessmemory, and this results in that one or more messages/commands are sentfrom the master onto the line system. In addition, data for theconsumption are stored in the master, so that the evaluation processgone through by the master before an action, also have a basis in theprevious consumption pattern in the individual dwelling.

From the life pattern of an end user, for example a water heater has agiven energy consumption profile. From this profile and thespecifications existing for such a water heater, calculations can bemade for the consumption during the twenty-four hours. For example, atank of 200 l uses about 2000 W when it is switched on. The heating timefor cold water to for example 60° C. is about three hours under normalconditions. When the water is heated, it will be above a giventemperature for a number of minutes after the tank has been switchedoff. Such considerations have been made for all electric products whichare to be monitored/controlled in the household or dwelling. Thehigh-power products are systemized and the program makes an evaluationof the consumption with reference to the time of the day, asf. Thus, thedata in the memory of the main unit are reduced to a system withreference to where and when the various incidents in the system occur.

The software which contains the set of rules for the system, and inwhich the external variables are inserted, will contribute to the systemgetting a lower risk in the evaluation process. The evaluations of themaster are influenced by the time of the real-time clock, temperature,historical energy consumption and the energy consumption at the moment.These parameters affect the program which then effects one or moreactions. The different loads are regulated from the program which isstored in the firmware program stored in the read only memory (ROM). Theread only memory stores firmware controlling the program and executingthe action, and it contains also other important information forcontrol. The random access memory (RAM) stores the temperature and theenergy consumption over time, which is also included in the evaluationprocess.

If it is desirable or of interest, the master 10 may also be arranged toreceive external signals as additional parameters for control of thesystem.

FIG. 6 shows a block diagram of a function node 4 or 5 in FIG. 3. Asappears, the node contains a processor unit (CPU) 30 capable of sendingand receiving signals so that the node is an intelligent unit. Similarlyto the master, each node has a quite special identity “ID” or address.The system has totally 64000 addresses, something which dictates thatthere may be 64000 electric units that can be controlled in a system.

To the processor unit 30 there is connected a memory 31 assisting thenode in remembering condition, functional range and so-called CEBuscontext. (“CEBus” designates the type of network used in the system tosee to it that each individual end user may communicate via the mains.)The processor unit 30 also controls a relay 32 causing the node to beable to connect a load of up to 16A. The node communicates on the mainsin the same manner as the master, and for this purpose the CPU unit isconnected to the mains via an SSC chip 33. The node is also shown tocontain a regulator 34 for current supply.

The main unit or master of the system in practice is mounted in the fusebox in the building where the system is to be installed. Since thecommand signals are transmitted over the mains, it is not necessary withnew installations in the form of new lines. In the contact point inwhich the electric unit to be controlled is plugged in, there isinstalled a node (receiver) which is to regulate when the product is tobe on or off, or is to be regulated in another manner. This node isencapsulated and may be installed in a concealed mounting in thebuilding, or it may be mounted as a plug-in unit (i.e. the node isplugged into the contact point, and the electric product is plugged intothe node).

As will be appreciated from the preceding description, the heart of theinvention is the “electronic power limiter” which enables load controlor release of power by means of coordination of all information which isput into the system and which is controlled by means of the set of ruleswhich has been set up and which forms part of the system software and isstored in the main unit (master).

The software will be able to be prepared by a person skilled in the artwhen the relevant set of rules and the remaining operational conditionsof the system have been settled. The software together with theabove-mentioned parameter data which are put in during operation of thesystem, enables the main unit to carry out a number of advantageousfunctions and operations during operation. Thus, in a suitableembodiment, the main unit is arranged to control connection anddisconnection of power-consuming units in chosen intervals according toaccidental circumstances when the power consumption is normal. It isalso appropriate that the main unit, when the power consuming unit isconnected under high load, provides for direct disconnection of anotherunit under given circumstances.

What is claimed is:
 1. An electronic system for controlling powerconsumption at a user of electric power, especially a dwelling orhousehold supplied with power from a power plant, comprising a controlunit (10) installed at the user and having a programmable memory (16)for storage of data for controlling the power consumption,parameter-sensing sensors (1, 2, 3, . . . ) for the supply of inputsignals to the control unit, an electric meter (11) communicating withthe control unit (10) for measuring the total instantaneous consumptionof the user, and a number of addressable function nodes (4, 5, 6)connected between the control unit (10) and the various loads (12) andbeing in both-way communication with the control unit, for connectionand disconnection of power-consuming units under the control thereof,the memory (16) of the control unit (10) containing a program forcontrolling the power consumption based on an estimate of theinstantaneous consumption, and the control unit (10) being arranged totransmit addressed messages to the function nodes (4, 5, 6), so thatonly the nodes with the correct address receive the current messages andexecute load-affecting actions based on the message content, to therebyreduce the instantaneous consumption, CHARACTERIZED IN that the controlunit (10) is a main unit arranged to control the power consumption alsobased on an estimate of a historical consumption pattern at the user, sothat the instantaneous consumption is reduced both in the periods inwhich the power load at the user is highest, and in the periods in whichthe historical consumption pattern of the user dictates that there is ahigh load, and that the main unit (10) is arranged to distribute thepower consumption by means of a random function distributing theconnection of the power-consuming units (12) over a given time interval,the random function being independent of energy plants and other users.2. A system according to claim 1, CHARACTERIZED IN that the main unit(10) is arranged to control connection and disconnection ofpower-consuming units (12) in chosen intervals according to accidentalcircumstances when the power consumption is normal.
 3. A systemaccording to claim 1, CHARACTERIZED IN that the main unit (10), when apower-consuming unit (12) is connected under high load, provides fordirect disconnection of another unit under given circumstances.
 4. Asystem according to claim 1, CHARACTERIZED IN that the main unit (10)and the function nodes (4, 5, 6) are arranged to carry out connectionand disconnection of the power-consuming units (12) in dependence ondifferent priority levels.
 5. A system according to claim 1,CHARACTERIZED IN that the main unit (10) is arranged to receive externalsignals as additional parameters for control of the system.